The aerodynamic design and integration of the jet-engine flow paths within next generation aircraft plays a major role in determining the capability and configuration of these aircraft. Next generation tailless aircraft, such as a blended wing body configuration, will have highly integrated propulsion flow paths which are buried or submerged into the platform. Such configurations often have significant boat-tail regions with aft-facing body surfaces that blend into the aft body and exhaust region. These aft-facing sloped surfaces often exhibit large adverse pressure gradients, flow field separation, and large-scale vortices. Additionally, exotic aperture shapes for the nozzle outlets may cause excessive propulsion performance losses. These losses may emanate from strong secondary flow gradients in the near wall boundary of the fluid flow, which produce large-scale vortical flow field structures. Aft body flow field detachments may produce increased aft body drag, aerodynamic buffeting, and jet wash heating. All of which comprise the integrity and capability of these aircraft.
In the past, adverse flow field vortical structures were avoided or addressed by the aircraft's design. For example, the overall aircraft could be lengthened to prevent massive aft body flow field detachments. Conventional large scale counter rotating vane vortex generators could be employed to address these flow field issues. Alternatively, the components in the path of the massive aft body flow field detachments may be structurally hardened (increasing weight) or replaced more frequently to avoid failures resulting from these stresses. Components in the path of these flow field structures may also be repositioned to non-optimal positions to reduce these stresses. However, these situations often results in reduced vehicle performance. Similarly, adding structural weight to support increased stress loads also result in reduced vehicle performance.
The aerodynamic design and integration of the jet-engine flow path plays a major role in determining the capability and configuration of aircraft such as the unmanned aerial vehicle (UAV), long-range strike (LRS), and multi-mission air mobility systems. To enable advances in vehicle design, groundbreaking aerodynamic technologies are required to integrate the propulsion nozzle flow path into these advanced all-wing platforms. Such technologies are required to meet more restrictive requirements for reduced weight/volume and mechanical complexity while aerodynamically accommodating exotic vehicle shaping requirements, without compromising functionality and performance.
These advanced jet engine flow paths may require vehicle-conforming (or conformal, compact, fixed-flow path, serpentine) designs with nozzles that provide thrust vectoring, throttling, and cooling capabilities. Aerodynamic design laws governing high-speed, viscous flow have limited integration of these next-generation designs required to meet the goals outlined for next generation aircraft. The Fixed-Wing Vehicle and Versatile Affordable Advanced Turbine-Engine initiatives are one example of such goals. New aerodynamic design solutions are required to integrate these exotic configurations into advanced vehicle aft bodies without seriously compromising vehicle design and capability.
To integrate these nozzles, previous solutions lengthen the vehicle aft fuselage to maintain a minimum aft body boat tail angle based on conventional aerodynamic design laws or used a shorter aft body length, but must live with the consequences of massive aft body flow field detachment or separation which produces increased aft body drag, aerodynamic buffeting, and jet wash heating, hence compromising vehicle capability.
New technology is therefore needed which will allow greater freedom to integrate advanced nozzle configurations while maintaining more compact aft body lengths by eliminating or mitigating the large-scale separated flow field zones and associated unsteady vortical flow field structures in the external nozzle/aft body region. The benefits of such a technology to aerodynamically “adapt” the flow field to aggressive nozzle/aft body integration designs for advanced platforms will be to enable reduced vehicle size and weight, favorable movement of vehicle center of gravity (Cg) forward, reduced drag, reduced aft body structural heating, and improved flight performance. Application of such a technology is not only limited to being a design enabler for future all-wing air-vehicle designs, but also could be applied to existing aircraft as a retrofit package for reducing drag, buffeting, and aft body heating.